Technical Field
This disclosure relates to a sheet folding device, an image forming system incorporating the sheet folding device, and a sheet folding method using the sheet folding device and the image forming system.
Related Art
As an example of sheet folding methods of performing a sheet folding operation to a sheet conveyed from an image forming apparatus, a leading end abutting method and a sheet holding and reversing method are known.
The leading end abutting method is a sheet folding method through which a sheet is firstly abutted against a stopper to adjust a sheet folding position and to form a warped portion of the sheet, and then the warped portion of the sheet is held in a sheet folding nip region, performed in a dedicated passage that is branched from a sheet conveyance passage through which the sheet is conveyed from an upstream device to a downstream device.
The sheet holding and reversing method is a sheet folding method through which sheet conveying members are rotated in a reverse direction while a sheet is supported between the sheet conveying members, so that a warped portion of the sheet is held in a sheet holding nip region, performed in a sheet conveyance passage through which the sheet is conveyed from an upstream device to a downstream device.
As can be seen from the above, the sheet holding and reversing method can do without including the dedicated passage that is branched from the sheet conveyance passage through which the sheet is conveyed from the upstream device to the downstream device. In addition, in the sheet holding and reversing method, the sheet folding position of the sheet is adjusted not by the stopper but by the rotation of the sheet conveying members disposed on a downstream side in the sheet conveying direction while the sheet conveying members are holding the sheet. Accordingly, a range of movement of the stopper may not be included in the sheet folding device and the image forming apparatus. Consequently, a reduction in size of the sheet folding device can be achieved.
There are some examples of a sheet folding device employing the sheet holding and reversing method that includes the above-described features.
As a first example, a sheet folding device includes a first pair of sheet conveying members that conveys a sheet, a second pair of sheet conveying members that receives the sheet conveyed by the first pair of sheet conveying members and further conveys the sheet, and a third pair of sheet conveying members that folds the sheet by rotating the second pair of sheet conveying members in the reverse direction in a state in which the first pair of sheet conveying members and the second pair of sheet conveying members are holding the sheet therebetween. In this configuration, one roller of the second pair of sheet conveying members also functions as one of the third pair of sheet conveying members.
As a second example, in the sheet folding device having the above-described configuration, the first pair of sheet conveying members and the second pair of sheet conveying members are driven by a single drive motor.
As a third example, a sheet folding device includes a first pair of sheet conveying members that folds a sheet, a second pair of sheet conveying members that receives the sheet folded by the first pair of sheet conveying members and further conveys the sheet, and a third pair of sheet conveying members that further folds the folded sheet. The second pair of sheet conveying members is rotatable in both directions, which are a forward direction and a reverse direction, while being driven for sheet conveyance. When the second pair of sheet conveying members is not driven for sheet conveyance, one direction of rotation of the second pair of sheet conveying members is locked while the other direction of rotation of the second pair of sheet conveying members is rotatable.
The first example employs the sheet holding and reversing method, that is, one roller of the second pair of sheet conveying members also functions as one of the third pair of sheet conveying members. According to this configuration, this sheet folding device achieves a reduction in size. When the second pair of sheet conveying members are rotated in the reverse direction while holding the sheet therebetween, a motor load significantly changes depending on paper size and thickness, and therefore the amounts of conveyance vary due to driving of the motor, and therefore it is likely that the sheet folding position is shifted.
By contrast, the respective sheet folding devices of the second and third examples employ a feedback control to control the driving of the motor, so that the sheet can be folded at a correct position.
The feedback control is performed to correct the variation in amounts of conveyance of a drive motor but is performed to basically correct a speed of conveyance when the speed is shifted. By correcting the speed of conveyance of the sheet, the variation in amounts of conveyance can be corrected. However, the positional shift causing the variation in amounts of conveyance is not directly corrected while the speed of conveyance of the sheet is controlled.